Polymer, resist composition and patterning process

Abstract

A polymer of which dissolution rate in an alkaline developer increases under the action of acid comprises recurring units having formulae (1) and (2) wherein R1, R2, and R4 are H or methyl, R3 is difluoromethyl or trifluoromethyl, and X is tertiary alkyl. A resist composition comprising the polymer has a high sensitivity and resolution, decreased pattern collapse during development, and minimized MEF and is best suited as micropatterning material for the VLSI manufacture.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] This non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2005-316400 filed in Japan on Oct. 31, 2005, the entire contents of which are hereby incorporated by reference.[0002] This invention relates to (1) novel polymers suitable for use as the base resin in resist compositions for lithographic micropatterning, (2) resist compositions comprising the same, and (3) a patterning process using the resist compositions. BACKGROUND OF THE INVENTION [0003] In the drive for higher integration and operating speeds in LSI devices, the pattern rule is made drastically finer. The rapid advance toward finer pattern rules is grounded on the development of a projection lens with an increased NA, a resist material with improved performance, and exposure light of a shorter wavelength. In particular, the change-over from i-line (365 nm) to shorter wavelength KrF laser (248 nm) brought about a significant innovation,...

AI Technical Summary

Benefits of technology

[0009] An object of the invention is to provide a chemically amplified positive resist composition which, when processed by photolithography, offers decreased pattern collapse during development, a minimized MEF, a significantly high contrast in alkaline dissolution rate before and after exposure, a high sensitivity, and a high resolution, so that it is suited as a micropatterning material for the manufacture of VLSI or the formation of photomask patterns.

[0012] The inventors have found that the effects of preventing the pattern collapse during development and minimizing the MEF are exerted when a polymer comprising an ester form having a specific fluorinated alkyl alcohol structure and an ester form having a tertiary alkyl ester structure is used as the base resin.

[0020] It is noted that immersion lithography can be applied to the resist composition of the invention. The ArF immersion lithography uses deionized water as the immersion solvent. The immersion lithography involves prebaking a resist film and exposing the resist film to light through a projection lens, with water interposed between the resist film and the projection lens. This technology, combined with a projection lens having a numerical aperture of at least 1.0, is important for the ArF lithography to survive to the 65 nm node, with a further development thereof being accelerated. The lactone ring, which is used as an adhesive group in the prior art ArF resists, has high affinity to water, allowing a problem to arise during immersion in water that more water penetrates into the resist from its-surface whereby the resist surface is swollen. By contrast, fluorinated alkyl alcohol has a solubility in alkaline aqueous solution, but a low affinity to neutral water. Thus, the influence of swelling due to immersion can be restrained by introducing a fluorinated alkyl alcohol structure into the base resin.

[0021] The resist composition of the invention allows the feature size of the pattern after development to be reduced by various shrinkage techniques. For example, the hole size can be shrunk by such techniques as thermal flow, RELACS, SAFIRE, and WASOOM. More effective shrinkage of hole size is possible particularly when the inventive polymer is blended with a ROMP polymer having a low Tg.

[0022] The resist composition comprising the polymer of the invention has a high sensitivity, high resolution, restrained pattern collapse during development, and minimized MEF. Thus the composition is best suited as micropatterning material for the manufacture of VLSI or the like.

Problems solved by technology

Since conventionally used novolac resins and polyvinylphenol resins have very strong absorption in proximity to 193 nm, they are difficult to use as the base resin for resists.

One factor causing the pattern collapse is swelling during development.

While the polyhydroxystyrene used as the resist for the KrF lithography, in which the phenol moiety is a weak acidic group and has an appropriate alkali solubility, is resistant to swelling, the ArF lithography uses polymers containing hydrophobic cycloaliphatic groups, which must be dissolved using carboxylic acids having a high acidity, leading to a likelihood for the polymers to swell during development.

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